Home networks are becoming more common and desirable for connecting computers within a home. One type of home network is the home phone line network which uses telephone lines typically installed in residence homes for communication between computers in the home.
FIG. 1 illustrates a home phone line network. The Home Phone Line Networking Alliance (HPNA) has published a specification to standardize the behavior of home phone line networks. The current HPNA specification is version 2.0 (“HPNA 2.0”). The network comprises a control chip 100. The chip 100 further comprises a Media Independent Interface (MII) 106, a Media Access Control (MAC) 108, and a Physical Layer (PHY) 110. The chip 100 implements HPNA 2.0. The chip 100 receives a signal containing data packets through the telephone wires via a phone jack 102. There is an analog front end (AFE) 104 which processes the signal between the chip 100 and the telephone wires. The chip 100 then processes the packets received in the signal from the AFE 104, and outputs a signal to the Host MAC 112.
Under HPNA 2.0, stations in the network supports a 10 megabits-per-second (mbps) data rate and/or a 1 mbps data rate, depending on the network state of the station. Such are referred to as “10M8 stations”. Stations implemented under a previous version of the HPNA specification (“HPNA 1.x”) supported only the 1 mbps data rate. Such stations are referred to as “1M8 stations”.
There are three possible network states for 10M8 stations: V1M2 mode, 1M8 mode, and 10M8 mode. 10M8 stations in the 1M8 mode transmit only 1M8 format frames, with a private communication (PCOM) field set to 1 or 2. The PCOM is a field in the frame. Its information is used by the PHY 110 in node-to-node communications. The PCOM field is set as follows:                PCOM=0 refers to a 1M8 station;        PCOM=1 refers to a 10M8 station functioning in V1M2 mode or 1M8 mode if V1_DETECTED is not asserted; and        PCOM=2 indicates a 10M8 station functioning in V1M2 mode or 1M8 mode if V1_DETECTED is asserted.        
The signal, V1_DETECTED, is described further below.
10M8 stations in the 10M8 mode transmit only 10M8 format frames. 10M8 stations in the V1M2 mode transmit either 1M8 format frames to 1M8 stations with a PCOM set to 1 or 2, or 10M8 compatible format frames to 10M8 stations. The 10M8 compatible frame contains a gap within the data frames. This “gap frame” provides interoperability between the format frames under HPNA 2.0 and HPNA 1.x.
The following equations set forth the three modes possible for a 10M8 station:V1M2_MODE:=(not ConfigV1) and ((not ConfigV2) or ConfigV1M2) and (ConfigV1M2 or V1_DETECTED or V1_SIGNALED)1M8_MODE:=ConfigV110M8_MODE:=not (V1M2_MODE or 1M8_MODE)
ConfigV1M2 is a signal which forces a station into the V1M2 mode. ConfigV1 is a signal which forces a station into the 1M8 mode. ConfigV2 is a signal which forces a station into the V1M2 mode.
V1_DETECTED is a signal which is asserted when a 10M8 station, while in 10M8 Mode and with Link Integrity Status=DOWN, detects a 1M8 format frame with a PCOM=1. V1_DETECED is also asserted when a 10M8 station detects a 1M8 format frame with a PCOM=0. The Link Integrity Status indicates whether or not the station is connected with another station. If the station is disconnected, then the Link Integrity Status=DOWN. If the station is connected, then the Link Integrity Status=UP.
V1_SIGNALED is a signal which is asserted when a 10M8 station detects or transmits a 1M8 format frame with a PCOM=2.
However, a problem occurs when the PHY 110 supports only the 1M8 and 10M8 modes, but not the V1M2 mode. This occurs when the PHY 110 does not support sending a 10M8 compatible frame and replacement of the PHY 110 is not viable.
Accordingly, there exists a need for a network state machine which supports the three network states of HPNA 2.0 using only two network states. The present invention addresses such a need.